BOLINA ALATA. 15 



Bolina alata Agass. 



Bolina alata Agass. Mem. Am. Acad., Vol. IV. Pt. 2, p. 349, Pis. 6, 7, 8. 1849. 



Bolina alata Agass. Contrib. Nat. Hist. U. S., Vol. HI. pp. 249, 289. 



AlcynOe vermicularis Gould (non Rang). Inverteb. of Mass., p. 349. 1841. 



Bolina alata Stimps. Mar. Inv. Grand Manan, p. 11. 1853. 



Bolina alata Packd. A List of Animals dredged near Caribou Island, Can. Nat. & Geol. 1863. 



It is quite remarkable that there should be no mention made by 

 Fabricius of a single Ctenophore which may be identified with any 

 species of the genus Bolina. There is hardly a more common Medusa 

 than the Bolina alata of our coast ; and the occurrence of so many of 

 our species of Gtenophoraa on the coast of Greenland makes the ab- 

 sence of Bolma the more striking, and quite interesting in a geograph- 

 ical point of view, as we should thus have among Acalephs a case of 

 geographical distribution analogous to that of Echiaarachnius, which 

 does not extend farther north than Labrador. 



To the description of the adult given by Professor Agassiz I have 

 nothing of importance to add, with the exception that the chymiferous 

 tubes which run along the edge of the lateral lobes, when seen from 

 the narrow side, should unite, and thus complete the circuit (Fig. 16), 

 instead of stopping short at a little distance apart, as they have been 

 represented by him. This connection takes place at an early period of 

 the development. (See Fig. 8.) 



The compression of the spherosome of Bolina and of Pleurobrachia 

 is in different planes, otherwise it would be exceedingly difficult to 

 distinguish a very young Pleurobrachia from a young Bolma. In the 

 young Bolina, as has been shown already by McCra- 

 dy, we find long tentacles ; so that the younger stages 

 of this Medusa are so unlike the adult, that it would 

 be the most natural error to commit, to consider it 

 the young of Pleurobrachia. The accompanying fig- 

 ures (1-3) are taken immediately after the escape of 

 the young from the egg. It will be noticed, when compared to Pleuro- 

 brachia, that besides the position of the tentacular organ, the outline of 

 the spherosome is somewhat different, and that the ambulacra are quite 

 narrow. The digestive cavity also fills a comparatively small space. 

 (Fig. 2.) The extreme tenuity of the tubes soon becomes a character 

 by which the young Bolina is at once distinguished from the young 

 Pleurobrachia, as well as its ellipsoid shape, which greatly increases 



-^'Mw' 



In all the young Ctenophorfe the following lettering has been adopted : d, digestive cavity ; 

 a, anal rosette ; t, tentacle ; c, long ambulacral tube (longitudinal ambulacra) ; c', short ambulacral 

 tube (lateral ambulacra) ; e, eye speck; /, funnel; o, ambulacral cavity; I, lateral tubes, c' is the 

 longest tube at first, and c the shorter ; n, lobes of spherosome ; the names are taken fi-om the adult. 



Fig. 1. Young Bolina, seen from the narrow side. 



